1. Field of the Invention
The present invention generally relates to a fabricating process for forming a flexible substrate, and more particularly, to a fabricating process for forming a flexible substrate for use in an organic electro-luminescence display, so as to overcome the problems such as the moisture during photolithography process and poor transparency of the photo-resist, reduce the pixel size and thus improve the reliability and resolution.
2. Description of the Prior Art
In recent years, the photo-electronic industry has become one of the most promising and competitive prospects. In particular, the organic electro-luminescence display (OELD) is considered the future flat display due to its outstanding characteristics such as self-lighting, high brightness, high resolution, and good contrast. However, the state-of-the-art technology related to the fabrication of such a display is still far from perfect, thus lots of efforts on research are under way.
The basic configuration of an organic electro-luminescence element is a laminated structure comprising a transparent conductive layer for the positive electrode, a metal electrode for the negative electrode, and an organic electro-luminescence (EL) layer sandwiched between the negative electrode and the positive electrode. A metal mask was used for fabrication. Nowadays. A photo-resist layer is commonly used, instead of the metal mask, in the industry. For example, the U.S. Pat. No. 6,025,894 discloses an organic electro-luminescence display, in which an organic electro-luminescence layer sandwiched between a front electrode and a back electrode is supplied with a driving voltage. And also, in the U.S. Pat. No. 6,165,384, there is provided a fluorescent dye composition for inclusion in a fluid for leak detection applications, which is responsive to a broad range of light sources.
Please refer to FIG. 1, which schematically illustrates the fabrication method in accordance with the prior art. To begin with, there is provided a substrate 10, on which a patterned transparent conductive layer 15 is formed by using indium tin oxide (ITO) or indium oxide as the positive electrode for emitting holes, as shown in FIG. 1A.
An interlayer 20 is formed on the transparent conductive layer 15, as shown in FIG. 1B. The interlayer 20 is an electron/hole transmitting layer (ETL/HTL), which helps to improve carrier transport.
Then, an organic layer 25 is deposited on the interlayer 20, as shown in FIG. 1C. The organic layer 25 is composed of an organic electro-luminescence material or a fluorescent dye composition. When a voltage is applied, a broad range of light is emitted from the organic layer 25 or the opposing surfaces of the organic layer 25.
Finally, a metal layer 30 is deposited on the organic layer 25, functioning as the negative electrode, as shown in FIG. 1D. The metal layer 30 is composed of inertial metal such as Al, In, Ag and Au, and is used as an electron emitting layer.
In addition, when a voltage is applied, the electric field causes the holes and the electrons to be emitted from the positive electrode and the negative electrode, respectively. The holes and the electrons recombine as excitons in the organic layer 25, and then the light is emitted due to exciton transition from the excited state to the ground state.
However, in the prior art, the substrate is made of glass, which is not suitable for displays with a curved surface. Moreover, when the organic material is employed, it often results in failure due to the moisture during photolithography process and poor transparency of the photo-resist. Furthermore, the metal lines fall off the substrate easily and it leads to shorter lifetime. Accordingly, the products thus made suffer from poor reliability and low fabrication yield for large-size display, which adversely affects the resolution.
Therefore, the present invention provides a fabricating process for forming a flexible substrate, which is used to overcome the problems in the prior art and improve the reliability and resolution.